• 한국정밀공학회지
• /
• 제16권11호
• /
• pp.148-157
• /
• 1999

The objective of this study is to investigate the effect of three main chemical compositions(Mg, Zn, Si) on extrudability of 7xxx Al alloy with high tensile strength. A few Al alloys based on 7xxx alloys were metal mold cast with various weight*%) of Mg 0.3-1.2%, Zn 5.0-8.0% and Si 0.4-0.7%, to envestigate the effects of extrudability, as well as mechanical properties. To measure the extrudability of cast billets, maximum extrusion pressure and surface temperature at die exit before tearing occurs were obtained by experiment and simulation of thermo-viscoplastic F.E.M. Also the yield and tensile strength of extruded products were tested.

• 대한치과보철학회지
• /
• 제30권3호
• /
• pp.411-436
• /
• 1992

The purpose of this study was to assess the adhesion of resilient denture liners (such as, heat-cured silicone molloplast B,cold- cured silicone Mollosil) to polymethyl metacrylate (K-33) and metal (Megalloy) in the laboratory by peel test. The resilient denture lines were processed according to manufactures instruction, onto prepared specimens(original resin base plate, rough resin base plate, stippled metal plate, mesh metal plate ) 75mm long and 25m wide. And then, the peel test was performed by instron. The results were as follows : 1. The bonding strength of Mollosil was stronger than that of Molloplast B except the specimen of stippled metal plate. 2. The tensile strength of Mollosil was weaker than that of Molloplast Bas tearing of Mollosil was occured in the peel test. 3. Mesh metal plate had the highest bonding strength in the case of Molloplast B and Mollosil. But stippled metal plate have high bonding strength in the case of Molloplast B and have the lowest bonding strength in the case of Mollosil. 4. The bonding strength of rough resin base plate was stronger than that of original resin base plate in the case of Molloplast B and Mollosil. 5. The bonding strength of metal plates was stronger than that of resin base plates in the case of Molloplast B and Mollosil except the case of bonding strength between the stippled metal plate and Mollosil. 6. It seems that the Increase of surface and retention form of metal plate and resin base plate produces higher physical bonding strength.

• 한국포장학회지
• /
• 제5권2호
• /
• pp.38-41
• /
• 1999

This study was carried out to investigate improvement of kraft paper sack mixed with recycled paper for sugars and assorted feeds. Four Plies of kraft paper mixed with recycled paper(basis weight : $80g/m^2$) were taken place of two plies of kraft paper made from all pulp(basis weight : $98g/m^2$) and one ply of kraft paper mixed with recycled paper(basis weight : $80g/m^2$) for sugar 30kg. Three Plies of kraft paper mixed with recycled paper(basis weight : $80g/m^2$) were taken place of two plies of kraft paper made from all pulp(basis weight $98g/m^2$) for sugar 15kg and assorted feed 25kg. Physical properties, tensile strength, internal tearing strength and bursting strength, were improved by exchanging kraft paper mixed with recycled paper for kraft paper from all pulp and so kraft paper sacks made from all pulp were no damage in handling. They had so high friction coefficient that there was no danger of collapse on pallet by slipperiness in transportation and handling. And they had high printability so disappearance of printing by the contact with other paper sack in transportation was not found.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2022년도 가을 학술논문 발표대회
• /
• pp.191-192
• /
• 2022

It was intended to evaluate whether the primer affects the physical performance of the waterproofing membrane coating. For this end, the physical performance change of the urethane waterproofing membrane coating was evaluated for urethane-based and polymer-based primers. As a result of the evaluation, it was confirmed that the type of primer may affect the physical performance of the waterproofing membrane coating. In particular, a difference in performance of more than 100% was confirmed in tensile strength and percentage elongation. Through these results, it was confirmed that the selection of the primer was important. In the future, follow-up studies on various waterproofing membrane coatings are needed.

• Structural Engineering and Mechanics
• /
• 제88권1호
• /
• pp.95-107
• /
• 2023

In this study, circular thin-walled reinforced high strength concrete-filled steel tube (RHSCFST) stub columns with various tube thicknesses (i.e., 1.8, 2.5 and 3.0mm) and reinforcement ratios (i.e., 0, 1.6%, 2.4% and 3.2%) were fabricated to explore the influence of these factors on the axial compressive behavior of RHSCFST. The obtained test results show that the failure mode of RHSCFST transforms from outward buckling and tearing failure to drum failure with the increasing tube thickness. With the tube thickness and reinforcement ratio increased, the ultimate load-carrying capacity, compressive stiffness and ductility of columns increased, while the lateral strain in the stirrup decreased. Comparisons were also made between test results and the existing codes such as AIJ (2008), BS5400 (2005), ACI (2019) and EC4 (2010). It has been found that the existing codes provide conservative predictions for the ultimate load-carrying capacity of RHSCFST. Therefore, an accurate model for the prediction of the ultimate load-carrying capacity of circular thin-walled RHSCFST considering the steel reinforcement is developed, based on the obtained experimental results. It has been found that the model proposed in this study provides more accurate predictions of the ultimate load-carrying capacity than that from existing design codes.

• 폴리머
• /
• 제32권3호
• /
• pp.270-275
• /
• 2008

고무재료의 피로균열 성장특성은 고무제품의 강도와 내구성을 평가하는 매우 중요한 요소이다. 본 연구에서는 자체 제작한 피로균열 성장 측정기를 이용하여 충전제 종류에 따른 EPDM의 피로균열 성장특성을 고찰하였다. 피로균열성장은 진동수와 측정온도에 영향을 받았으며, 진동수가 증가함에 따라 균열성장속도는 감소하였고 온도가 증가함에 따라 균열성장속도는 증가하였다. 충전된 EPDM의 인열에너지와 균열성장속도의 상관관계는 지수법칙을 따랐으며, 충전제의 함량이 증가함에 따라 균열성장속도가 감소하였다. 또한, 실리카로 충전된 EPDM이 카본블랙으로 충전된 EPDM에 비해 더 우수한 피로저항 특성을 보였다. 실리카로 충전된 경우, 균열성장속도는 30 phr까지 감소하다가 그 이후 다시 증가하였다. 미충전 시편의 피로 파괴단면 SEM 사진에서 작고 유연한 파괴자국들이 관찰되었으며, 실리카가 충전된 시편의 단면에서는 보강효과로 인하여 인열 형태가 불규칙 적이고 비교적 거친 표면이 관찰되었다.

• 한국재료학회지
• /
• 제5권8호
• /
• pp.953-959
• /
• 1995

분말야금법으로 제조된 A6061기 입자분산강화 복합재의 열간압술가공에 있어서 압출특성에 미치는 강화입자의 종류, 빌렛특성 및 암술조건의 영향에 대하여 조사하였다. A6061기 복합재료의 열간 압술 전단 변형저항에 미치는 강화입자종류의 영향은 Si $C_{w}$ > A1$_2$ $O_{3f}$ > A1$_2$ $O_{3f}$ > Si $C_{p}$의 순으로 되었으며, 모든 강화입자에서 부피분율이 증가함에 따라서 Kw값도 증가하였다. 압출조건, 강화입자의 첨가량 및 첨가입자의 평균입도에 관계없이 A1$_2$ $O_{3p}$가 첨가된 복합재의 열간압출가공에 필요한 소요압력은 Si $C_{p}$의 경우보다 컸다. 압출압력은 압출 다이스 반각이 커질수록 감소하는 경향은 나타났다. 이것은 다이스 반각에 의해 생성되는 빌렛과의 접촉면적이 증가하여 전단마찰응력(m $k_3$)이 상승하기 때문이다. 압출시 압출온도 상승은 저온에서 ~$50^{\circ}C$ 정도 증가하였으며, 압출온도가 50$0^{\circ}C$ 이상이 되면 압출재 표면에 극심한 tearing이 발생하였다. 강화입자의 첨가량이 증가할수록 이 현상은 더 심하게 되었다.게 되었다.

• 한국염색가공학회지
• /
• 제32권3호
• /
• pp.176-183
• /
• 2020

In order to study wearable air cushion materials capable of responding to massive impact in high-altitude fall situation, high tenacity woven fabrics were bonded by heat only depending on various type of thermoplastic films and then mechanical properties were measured. Tensile strength, elongation, and 100% modulus measurement results for 4 types of films show that TPU-2 has higher impact resistance and easier expansion than PET-1. After thermal bonding, the combination with the highest tensile strength was a material with a TPU-2 film for nylon and a PET-2 film for PET, so there was a difference by type of fabric. The tear strength of the bonded materials were increased compared to the fabric alone, which shows that durability against damage such as tearing can be obtained through film adhesion. All of the peel strengths exceeded the values required by automobile airbags by about 5 times, and the TPU-2 bonded fabric showed the highest value. The air permeability was 0 L/dm2 /min. For both the film and the bonded material, which means tightness between the fabric and the film through thermal bonding. It is expected to be applied as a wearable air cushion material by achieving a level of mechanical properties similar to or superior to that of automobile airbags through the method of bonding film and fabric by thermal bonding.

• 한국염색가공학회지
• /
• 제29권1호
• /
• pp.18-24
• /
• 2017

Meta-aramid fabric has been widely used as the reinforcement of composites due to its high flame resistance and tearing strength. Functionality such as abrasion resistance of fabric is very important for specialty fabrics used in car racing suits. In this study, to improve abrasion resistance property of meta-aramid fabric, silicon deposition was conducted by utilizing RF magnetron sputtering. The sputtering process parameters effects were investigated as sputtering power and substrate temperature. The obtained results suggest that the silicon deposition on the meta-aramid fabric has obvious effect upon increasing the abrasion resistance, the thermal insulation and the electric resistance condition for silicon deposition was established. In conclusion, the results of this study have made it possible to manufacture meta-aramids with higher abrasion strength.

• 한국주조공학회지
• /
• 제18권6호
• /
• pp.570-577
• /
• 1998

An investigation has been conducted to describe solidification characteristics in Sn-Zn binary system and Sn-Zn-Ag ternary system added by Ag produced by the continuous casting process using heated mold as a basic study for developing Pb-free solder materials. To obtain the continuous casting rods with mirror surface and near net shape at higher casting speed, water flow rates must be increased and mold temperature must be lowered. However, surface tearing in the casting rods occured at lower continuous casting speed while break out occured at higher continuous casting speed even if optimum conditions such as water flow rate and heated mold temperature are determined. Primary ${\alpha}Sn$ and eutectic structure in unidirectioally solidified Sn-Zn alloys were finer with increased casting speed. But, directionality may not be expected for primary Zn in hypereutectic Sn-Zn alloy. It was found that the addition of $0.2{\sim}0.8%$ Ag promoted the growth of primary ${\alpha}Sn$ dendrites. The changes of tensile strength and elongation in Sn-Zn binary alloys were not observed while the increase of tensile strength and the decrease of elongation in Sn-Zn-Ag ternary alloys were observed with increased casting speed.